Reheat vapor generator

ABSTRACT

This invention relates to a method for increasing the superheated output flow of a reheat type vapor generator by apportioning additional saturated vapor flow between the superheater and resuper-heater and sizing each accordingly rather than sizing each for the total increase in saturated vapor flow. Such vapor generators can be utilized for example in reheat type steam generators supplying turbines of high, intermediate and low pressure sections for the purpose of meeting short duration electrical demand.

United States Patent Miliaras REHEAT VAPOR GENERATOR [76] Inventor: Emmanuel Stephen Miliaras, 12 Mount Pleasant St., Winchester, Mass. 01890 [22 Filed: Apr. 10,1973 211 Appl.No.:349,790

52 us. Cl. so/ sss, 60/662 [51] im. Cl. F0ld 13/02,""F01i 27700 [58] Field of Search 60/70, 104; 122/479 [56] References Cited UNITED STATES PATENTS 4/1944 Meyer et al 60/104 X 2/1951 Reese et al. 60170 X l 1/1957 Eggenberger 60/70 X 3,826,093 July 30, 1974 Primary Examiner-Edgar W. Geoghegan Assistant ExaminerH. Burks, Sr.

[ 5 7] ABSTRACT This invention relates to a method for increasing the super-heated output flow of a reheat type vapor generator by apportioning additional saturated vapor flow between the superheater and resuper-heater and sizing each accordingly rather than sizing each for the total increase in saturated vapor flow. Such vapor generators can be utilized for example in 'reheat type steam generators supplying turbines of high, intermediate and low pressure sections for the purpose of meeting short duration electrical demand.

5 Claims, 1 Drawing Figure 1 REHEAT VAPOR GENERATOR The present invention relates to reheat type vapor generators, where the superheated output flow after having once been utilized, as for example, when partially expanded through a turbine section, is again resuperheated.

Super vapor generators are the reheat type steam generators utilized to drive electrical turbogenerators or propulsion turbines in marine powerplants.

The maximum output of a vapor generator. is usually determined by the flow than can be admitted through the first stage turbine area at the rated conditions of steam pressure and temperature. The output of the turbine can be considerably increased, other design factors being satisfied, by admitting more steam downstream of the first turbine stage or at such more convenient points as the inlet of the first and second reheat turbine sections;. another means of increasing turbine output is by shutting off feedwater heaters and increasing steam flow through the lower pressure turbine sections.

Where a temporary increase in the energy supplied to the turbine is desirable and the steam generator has not been accordingly oversized,'recourse to storing preheated feedwater or steam, or external to the steam generator preheating of feedwater has been proposed, and methods for increasing vapor generator output by increasing heat input in the economizer are described in U.S. Pat. No. 3,485,048.

In power plants equipped with a reheat type steam generator, the saturated steam is superheated in the steam-generators superheater and after partial expansion in the high pressure turbine section returned to the steam generator for resuperheating in the reheater, but for a minor portion occasionally extracted to a high pressure feedwater heater or used in an auxiliary turbine drive. in such reheat type steam generators, superheater and reheater are sized essentially for the saturated steam flow that is generated and an increase in the steam generators output entails a commensurate increase in superheater and reheater size.

The present invention provides for the utilization of increased saturated steam flow without a commensurate increase in cost and poor part load performance of the superheater and reheater.

The applicability of the inventibn is not limited to fossil fired steam generators but to all vapor generators that include a resuperheating section, irrespective of the medium and the source of the heat supplied to the vapor generator or the use of the superheated and resuperheated vapor.

The means for the utilization of an increase in a steam generators saturated steam flow with less than commensurate increase in .superheater and reheater size are set forth below and described wtth reference to FIG. 1 which is a diagrammatic illustration of a reheat type fossil fired steam generator embodying the present invention, and the associated power plant equipment.

The vapor generator comprises a furnace 6 and flue gas path enclosure 7 (both of which may be subdivided), lined with closely spaced water cooled or water and steam cooled tubes 8, fuel burners 9, additional fuel burner 16 for increased heat input to the economizer, steam superheating tube bundles a,

resuperheating tube bundles 10b, and economizer tubes 12.

Associated power plant equipment shown in FIG. 1 are: a high pressure turbine section 30, intermediate and low pressure turbine section receiving reheated steam 31, the electrical generator coupled to the turbine 32, the condenser 34, closed feedwater heaters 35, valves controlling the steam extraction flow to the heaters 37, a deaerating heater 36, bypass valve 33 between the inlet of the high pressure turbine section 30 and the intermediate and low pressure section 31, bypass yalye 44 allowing saturated steam, after throttling, directly to the inlet of the reheater 10b and electrical demand sensor and generation dispatching device 38. 5

The operation of the vapor generator utilizing the invention and the associated power plant is envisaged along the following lines:

Upon a signal to device 38 of increased electrical demarid and the sendout by the device of the appropriate signals, additional saturated steam flow is generated, for example by increased firing in burners 9 or additional heat input to the economizer through burner 16, the increase in saturated steamflow divided or otherwise proportioned by operating valve 44 to allow part of the increased flow to the inlet of the reheater 10b to be superheated there and hence to the inlet of intermediate and low pressure turbine section 31, the remaining part of the increase in saturated steam flow after flowing through superheater 10a also admitted to the inlet of intermediate and low pressure section 31 by the operation of bypass valve 33, the total of the increase in saturated steam flow in this case bypassing high pressure turbine section 30.

The total of the increase in saturated steam flow need not bypass the high pressure turbine section. Fraction of the increase in the saturated steam flow to the superheater may be admitted to the high'pressure turbine section at the first stage or subsequent stages, such fraction of the flow continuing through the vapor generators reheater, accordingly sized.

The terms and expressions which have been employed in presenting the invention and its embodiments are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown or described therein. But it is recognized that various modifications and combinations of the features mentioned are possible or desirable, as the constraints of an existing vapor generator modified to utilize the invention will indicate.

Other embodiments will be apparent to those skilled in the art and are within the following claims:

What is claimed is:

1. For a reheat type vapor generator having a given designed continuous rating and supplying the high pressure and intermediate pressure sections of a power genresuperheating section to the inlet of the intermediate pressure turbine section, a secondary system designed to increase flow to the intermediate pressure turbine section, including an inlet located in the second output line to the intermediate pressure turbine section, and means for electively operating and securing said secondary system, said secondary system comprising means for dividing and conveying an increase in saturated vapor flow above the vapor generators rated output from the vapor generating section to the superheating section and the resuperheating section, whereby the increase in flow to the intermediate pressure turbine section can increase the power generated by the turbine at peak demand, above the output corresponding to the continuous rating'of said vapor generator.

2. The combination .of claim 1 wherein said inlet in the 'second'output line comprises a conduit between the passage conducting saturated vapor from the vapor generating section to the superheating section and means for electively operating and securing said conduit, including valves for proportioning and throttling the flow of steam. h

3. The combination of claim 2 including a supplementary conduit between the first output line and the second output line and means for electively operating and securing said supplementary conduit including valves for proportioning and throttling the flow of steam.

4. The combination of claim 3 wherein part of the steam flow through the first output line to the high pressure turbine section is admitted to said high pressure section downstream of the first turbine stage.

5. The method of operating a reheat vapor generator that comprises a vapor generating section, a superheating section and a resuperheating section, comprising, upon the existence of a peak demand condition, means for conveying part of an increase in saturated vapor flow to the resuperheating section. i I 

1. For a reheat type vapor generator having a given designed continuous rating and supplying the high pressure and intermediate pressure sections of a power generating reheat type turbine, said vapor generator comprising a vapor generating section, a superheating section and a resuperheating section, water passages introducing feed water to said vapor generating section and steam passages for conducting steam from said vapor generating section to said superheating section and from said superheating section to a first output line to the inlet of the high pressure turbine section, return line from the exhaust of said high pressure turbine section to the vapor generator''s resuperheating section and a second output line from the vapor generator''s resuperheating section to the inlet of the intermediate pressure turbine section, a secondary system designed to increase flow to the intermediate pressure turbine section, including an inlet located in the second output line to the intermediate pressure turbine section, and means for electively operating and securing said secondary system, said secondary system comprising means for dIviding and conveying an increase in saturated vapor flow above the vapor generator''s rated output from the vapor generating section to the superheating section and the resuperheating section, whereby the increase in flow to the intermediate pressure turbine section can increase the power generated by the turbine at peak demand, above the output corresponding to the continuous rating of said vapor generator.
 2. The combination of claim 1 wherein said inlet in the second output line comprises a conduit between the passage conducting saturated vapor from the vapor generating section to the superheating section and means for electively operating and securing said conduit, including valves for proportioning and throttling the flow of steam.
 3. The combination of claim 2 including a supplementary conduit between the first output line and the second output line and means for electively operating and securing said supplementary conduit including valves for proportioning and throttling the flow of steam.
 4. The combination of claim 3 wherein part of the steam flow through the first output line to the high pressure turbine section is admitted to said high pressure section downstream of the first turbine stage.
 5. The method of operating a reheat vapor generator that comprises a vapor generating section, a superheating section and a resuperheating section, comprising, upon the existence of a peak demand condition, means for conveying part of an increase in saturated vapor flow to the resuperheating section. 